Conventionally, the copy processing whose copy source and copy destination are specified by addresses is performed by reading data from the copy source address and writing the data to the copy destination address.
One of the methods for shortening the processing time for this type of copy processing is using caches accessible in a short time and performing copy in the caches. By this method, when the relevant copy processing is completed, even before writing the data to the copy destination disk, the data can be accessed from the host device.
As another technology related to the internal copy function, the technology of, when performing the copy processing in units of logical volumes, reporting the completion of the relevant copy processing to the host device before completing the copy processing and then performing the copy processing in the background exists.